Horner syndrome DDx


The features of Horner syndrome are:

  • Mild ptosis — paresis of Müller muscle (absent on upward gaze due to intact CN3 function)
  • Miosis — paralysis of pupillary dilator muscle
  • Ipsilateral anhidrosis
  • Apparent enophthalmos
  • Heterochromia iridis — may be present in congenital Horner syndrome
  • Lower eyelid reverse ptosis
  • The eye may appear slightly bloodshot due to loss of vasoconstrictor activity in the vessels of the bulbar conjunctiva.

The potential causes are numerous and fall into 3 categories:

  • Central lesions (expect anhydrosis of the upper forequarter and coexistent neurological deficits)
  • Preganglionic lesions
  • Postganglionic lesions (may not affect sweating — main sympathetic outflow to facial vessels and sweat glands is from below the superior cervical ganglion)


Central lesions (expect anhydrosis of the upper forequarter and coexistent neurological deficits)

Hemisphere lesions

  • hemispherectomy
  • massive infarction  of one hemisphere
  • thalamic hemorrhage
  • hypothalamic hemorrhage or infarct

Brainstem lesions

  • Vascular events (ischemia or hemorrhage), e.g. Wallenberg syndrome (lateral medullary syndrome)
  • Tumor, e.g. pontine glioma
  • syringobulbia
  • demyelination, e.g. multiple sclerosis
  • encephalitis

Neck lesions

  • central cord lesions
    • syringomyelia (can cause bilateral Horner syndrome)
    • tumors e.g. ependymoma, glioma
    • central cord syndrome due to trauma
    • arteriovenous malformation

Preganglionic lesions

lesions of cervico-thoracic spinal roots

  • cervical ribs
  • aortic aneurysms
  • avulsion of the lower brachial plexus (e.g. Klumpke’s paralysis)
  • severe cervical osteoarthritis with impingement from bony spurs (rare)
  • AVM

apical lung disease (some repetition — but a useful category to remember)

  • vascular anomalies
  • Pancoast’s apical lung tumor
  • iatrogenic (chest tube, central catheter)
  • infection (eg. apical TB)

cervical sympathetic chain lesions

  • local trauma and surgery e.g. thyroidectomy
  • tumours
    • Apical lung tumor (Pancoast tumor — usually squamous cell carcnoma)
    • metastases
    • thyroid tumours
    • neurofibroma
    • children — neuroblastoma, lymphoma, metastasis

Postganglionic lesions (may not affect sweating — main sympathetic outflow to facial vessels and sweat glands is from below the superior cervical ganglion)

Neck lesions affecting the superior cervical ganglion

  • tumours — e.g. thyroid
  • trauma
  • surgery (e.g. tonsillectomy)
  • degenerative or inflammatory spinal disease

Carotid artery lesions

  • spontaneous or traumatic dissection of the carotid artery
  • carotid aneurysm
  • carotid thrombosis
  • pericarotid tumours (Raeder paratrigeminal syndrome (ie, paratrigeminal neuralgia))

Base of skull/ carotid canal

  • tumor (nasopharyngeal CA)
  • trauma

Headache syndromes

  • Cluster headaches
  • Migraines

Middle ear (close proximity to the internal carotid artery, alongside which the sympathetic fibers run)

  • infection, e.g. otitis media
  • tumor e.g. cholesteatoma

Cavernous sinus

  • tumour, e.g. pituitary tumours such as prolactinoma
  • inflammation — Tolosa-Hunt syndrome
  • cavernous carotid fistula or aneurysm
  • cavernous sinus thrombosis

CCC Differential Diagnosis Series


Anosmia, Ataxia, Blepharospasm, Bulbar and Pseudobulbar palsy, Central Pontine Myelinosis, Cerebellar Disease, Chorea, Cranial nerve lesions, Dementia, Dystonia, Exophthalmos, Eye trauma, Facial twitches, Fixed dilated pupil, Horner syndrome, Loss of vision, Meningism, Movement disorders, Optic disc abnormality, Parkinsonism, Peripheral neuropathy, Radiculopathy, Red eye, Retinal Haemorrhage, Seizures, Sudden severe headache, Tremor, Tunnel vision


Bronchial breath sounds, Bronchiectasis, High airway pressures, Massive haemoptysis, Sore throat, Tracheal displacement


Atrial Fibrillation, Bradycardia, Cardiac Failure, Chest Pain, Murmurs, Post-resuscitation syndrome, Pulseless Electrical Activity (PEA), Pulsus Paradoxus, Shock, Supraventricular tachycardia (SVT), Tachycardia, VT and VF, SVC Obstruction


Abdominal distension, Abdominal mass, Abdominal pain, Asterixis, Dysphagia, Hepatomegaly, Hepatosplenomegaly, Large bowel obstruction, Liver palpation abnormalities, Lower GI haemorrhage, Malabsorption, Medical causes of abdominal pain, Rectal mass, Small bowel obstruction, Upper GI Haemorrhage


Genital ulcers, Groin lump, Scrotal mass, Urine colour, Urine Odour, Urine transparency


Arthritis, Shoulder pain, Wasting of the small muscles of the hand


Palmar erythema, Serious skin signs in sick patients, Thickened Tethered Skin, Leg ulcers, Skin Tumour, Acanthosis Nigricans


Diabetes Insipidus, Diffuse Goitre, Gynaecomastia, Hirsutism, Hypoglycaemia, SIADH, Weight Loss




Floppy infant 


Anaphylaxis, Autoimmune associated diseases, Clubbing, Parotid Swelling, Splinter haemorrhages, Toxic agents and abnormal vitals, Toxicological causes of cardiac arrest


CHEST: Atelectasis, Hilar adenopathy, Hilar enlargement on CXR, Honeycomb lung, Increased interstitial markings, Mediastinal widening on mobile CXR, Pulmonary fibrosis, Pseudoinfiltrates on CXR, Pulmonary opacities on CXR,
Gas on abdominal X-ray, Kidney mass,
Intracranial calcification, Intracranial structures with contrastVentriculomegaly,
OTHER: Pseudofracture on X-Ray


LOW: Anaemia, Hypocalcaemia, hypochloraemia, Hypomagnesaemia

HIGH: Bilirubin and Jaundice, HyperammonaemiaHypercalcaemia, Hyperchloraemia, Hyperkalaemia, Hypermagnesaemia

ACID BASE: Acid base disorders, Resp. acidosis, Resp. alkalosis,

Creatinine, CRP, Dipstick Urinalysis, Laboratory Urinalysis, Liver function tests (LFTs), Pleural fluid analysis, Urea, Urea Creatinine Ratio, Uric acid, Urinalysis, Urine Electrolytes


CCC 700 6

Critical Care


Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.

After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.

He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE.  He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.

His one great achievement is being the father of three amazing children.

On Twitter, he is @precordialthump.

| INTENSIVE | RAGE | Resuscitology | SMACC

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